Understanding the biology of the adipocyte life cycle is crucial to understanding the roles adipocytes and their constituent fatty acids play in health and disease processes. Specifically we propose that the aging large adipocyte lifecycle stage is pathogenic. Omega-3 fatty acids offer several health benefits and are known to reduce adipocyte cell size. Our hypothesis is that genetically optimizing omega-3 fatty acid concentrations in adipocyte fat stores will provide a mouse model capable of radically improving the pathogenic state of aging/large adipocytes. We predict that adipocyte derived omega-3 fatty acid concentrations will directly affect the adipocyte lifecycle, with respect to aging, apoptosis, cell size, and rates of lipolysis and lipogenesis. These changes will have profound beneficial effects on disease processes involving insulin resistance, and dyslipidemia. The goal of this project is to create and characterize a novel transgenic mouse model that optimally synthesizes omega-3 fatty acids as a result of adipocyte-specific expression of the C. elegans omega-3 fatty acid desaturase gene, known as fat-l. Specific aims include: Aim 1. Create adipocyte/fat-1 transgenic mice. (a) Prepare gene construct using the adipocyte protein 2 (aP2)-promoter/enhancer controlling the fat-1 cDNA, (b) Produce aP2-fat-1 transgenic mice by pro-nuclear microinjection on the C57BL/6 mouse background. (c) Genetically characterize multiple founder lines of aP2- fat-1 transgenic mice for transgene copy number and germ-line transmission. Aim 2: Characterize adipocyte/fat-1 transgenic mice. (a) Demonstrate tissue-specific expression of fat-1 by northern analysis of steady-state RNA. (b) Evaluate body fat mass by direct carcass analysis. (c) Confirm fat-1 activity by measuring changes in serum and tissue fatty acids and functional endpoint changes confirming the direct action by the increased omega-3 fatty acids on fat metabolism. Creating this model will dramatically increase the understanding of the pathogenic aging/large adipocyte life cycle stage and catalyze the development of novel treatments for metabolic diseases such as insulin resistance, type 2 diabetes, obesity, familial and acquired lipodystrophy disorders. This unique model will allow specific evaluation of the benefits adipocytes with optimal concentrations of omega-3 fatty acids, without the confounding factors of diet.